This application is a 371 of PCT/GB00/00099 filed Jan. 14, 2000.
This invention relates to vascular damaging agents and particularly to the use of new and known substituted benzimidazoles in the preparation of medicaments for the treatment of diseases involving neovascularisation.
Formation of new vasculature by angiogenesis is a key pathological feature of several diseases (J Folkman, New England Journal of Medicine 333, 1757-1763 (1995)). For example, for a solid tumour to grow it must develop its own blood supply upon which it depends critically for the provision of oxygen and nutrients; if this blood supply is mechanically shut off the tumour undergoes necrotic death. Neovascularisation is also a clinical feature of skin lesions in psoriasis, of the invasive pannus in the joints of rheumatoid arthritis patients and of atherosclerotic plaques. Retinal neovascularisation is pathological in macular degeneration and in diabetic retinopathy. In all these diseases reversal of neovascularisation by damaging the newly-formed vascular endothelium is expected to have a beneficial therapeutic effect.
5(6)-Substituted benzimidazole-carbamates are known and have found use as antiparasitic agents (P. J. Islip in Burgers Medicinal Chemistry (M. E. Wolff ed.), Fourth Edition, Part II, p481, (1979)). Examples of such compounds include mebendazole, fenbendazole, oxibendazole, flubendazole, albendazole, cyclobendazole, parbendazole, dribendazole, luxabendazole, and etibendazole. Their mode of action for their antiparasitic action is believed to involve selective binding to tubulin of the target parasite while having little effect due to binding tubulin of the mammalian host (Biochim. Biophys. Acta 630, 271-278, (1980)). Some of these compounds have been shown to be antimitotic for cancer cells and one particular 5(6)-substituted benzirnidazole-2-carbamate, nocodazole, has therefore been studied as an anticancer agent (Cancer Research, 36, 905-916 (1976)). No effects on neovasculature have been reported for any of these compounds.
Some structurally-unrelated compounds which bind tubulin have been shown to have anti-vascular effects when given at their maximum tolerated dose (MTD) (S. A. Hill et al. Eur. J Cancer, 29A, 1320-1324 (1993)) but other tubulin-binding agents, such as docetaxel, have no vascular-damaging activity even when administered at the MTD. The presence of tubulin-binding properties is then not predictive for antivascular activity.
According to the present invention there is provided the use of 5(6)-substituted benzimidazole-2-carbamates for the preparation of compositions for the treatment of diseases involving angiogenesis in which the 5(6)-substituted benzirnidazole carbamate has the formula 
wherein
Alk is an alkyl group
X is oxygen, sulphur, sulphinyl, sulphonyl, carbonyl (CO), thiocarbonyl (CS), sulphonyloxy, NH, iminomethylene (Cxe2x95x90NH), N-hydroxyiminomethylene, N-alkoxyimninomethylene, dialkoxymethylene, 1,3-dioxolan-2yl, 1,1-ethenyl, a group CHR3 or a bond
R1 is hydrogen, alkylarninocarbonyl or alkoxycarbonyl
R2 is hydrogen, alkoxycarbonyl, cyanomethyl, cyanoethyl, alkoxymethyl or acetoxymethyl.
R3 is hydrogen, hydroxy, alkoxy or amino
A is an optionally substituted aromatic, optionally substituted heteroaromatic, optionally substituted heterocycloalkyl, optionally substituted alkyl or optionally substituted cycloalkyl group
and the pharmaceutically acceptable salts, solvates and hydrates thereof.
Particular substituents that may be present on the group A include one or more substituents selected from a group Y, optionally substituted alkyl,(where substituents on such alkyl group may include one or more selected from hydroxy, amino, alkylamino, dialkylamino, halogen, carboxyl, SO3H, sulphate, phosphate, alkoxycarbonyl, aralkoxycarbonyl, alkoxycarbonylamino, aminoalkylaminocarbonyl and cyano), halogen, hydroxy, amino, alkoxy, alkylthio, cyano, nitro, sulphate, isothiocyanate, aryl, heteroaryl and heterocycloalkyl.
Y is a group selected from phosphate, alkylphosphate, C(O)R4, OC(O)R4, SO2R4, NHC(O)R4, NR5C(O)R4, SR4, S(O)R4, OSO2R4, NHSO2R4, NR5SO2R4, SO3H, CO2H and CO2R5 where R4 is a group selected from hydrogen, R5, OR5, NHR5, NR5R6, aryl, heteroaryl or heterocycloalkyl such aryl, heteroaryl or heterocycloalkyl groups being optionally substituted with one or more substituents selected from alkyl, heterocycloalkyl, haloalkyl, hydroxy, nitro, cyano, amino, alkylamino, dialkylamino, halogen, carboxyl, SO3H, sulphate and phosphate. R5 and R6, which may be the same or different, are each an alkyl group optionally substituted with one or more substituents selected from hydroxy, amino, alkylamino, dialkylamino, guanidino, halogen, carboxyl, SO3H, sulphate, phosphate, aryl and heteroaryl.
Some of the compounds usable in the invention are known, for example the following compounds within the following formula: 
These compounds are
Certain of these compounds are novel. In one embodiment the novel compounds are those of formula I in which at least one of the substituents on the group A is a group Y where Y is as hereinbefore defined. Particularly preferred are compounds defined by the formula 
wherein
alk is an alkyl group
B is an aromatic or heteroaromatic ring
X is oxygen, sulphur, sulphinyl, sulphonyl, carbonyl (CO), thiocarbonyl (CS), sulphonyloxy, NH, iminomethylene (Cxe2x95x90NH), N-hydroxyiminomethylene, N-alkoxyiminomethylene, dialkoxymethylene, 1,3-dioxolan-2yl, 1,1-ethenyl, a group CHR3 or a bond
R1 is hydrogen, alkylaminocarbonyl or alkoxycarbonyl
R2 is hydrogen, alkoxycarbonyl, cyanomethyl, cyanoethyl, alkoxymethyl or acetoxymethyl
R3 is hydrogen, hydroxy, alkoxy or amino
Y is as hereinbefore defined
R7 and R8 are each independently H, alkyl, halogen, hydroxy, amino, alkylamino, dialkylamino, alkoxy, alkylthio, cyano, nitro, or trifluoromethyl
with the proviso that Y is not NHC(O)Me and when B is a thiophene ring then Y is not C(O)CF3 and when B is a 5(6)-benzimidazole ring then Y is not NHCO2Me or NHCO2Et
and the pharmaceutically acceptable salts, solvates, hydrates and prodrugs thereof.
As used herein the term xe2x80x9calkylxe2x80x9d, alone or in combinations, means a straight or branched-chain alkyl group containing from one to seven, preferably a maximum of four, carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl and pentyl. Examples of alkoxy groups are methoxy, ethoxy, propoxy, isopropoxy, butoxy and t-butoxy. The term xe2x80x9chalogenxe2x80x9d means fluorine, chlorine, bromine or iodine. The term xe2x80x9carylxe2x80x9d as used herein unless otherwise stated includes reference to a C6-10 aryl group which may, if desired, carry one or more substituents selected from halogeno, alkyl, haloalkyl, alkoxy, hydroxy, amino, nitro and cyano. The term xe2x80x9caralkoxyxe2x80x9d means an alkoxy group substituted with an aryl group.
The term heteroaryl is defined herein as a mono- or bi-cyclic aromatic group containing one to four heteroatoms selected in any combination from N, S or O atoms and a maximum of 9 carbon atoms. Examples of heteroaryl groups include pyridyl, pyrimidyl, furyl, thienyl, pyrrolyl, pyrazolyl, indolyl, benzofuryl, benzothienyl, benzothiazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, triazolyl, quinolyl and isoquinolyl groups.
The term heterocycloalkyl includes heterocycloalkyl groups containing 3-6 carbon atoms and one or two oxygen, sulphur or nitrogen atoms. Particular examples of such groups include azetidinyl, pyrrolidinyl, piperidinyl, homopiperidinyl, piperazinyl, homopiperazinyl, morpholinyl or thiomorpholinyl groups.
The term cycloalkyl means a cycloaliphatic group containing 3-10 carbon atoms such as, for example, cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl.
One particularly preferred group of compounds are those of formula II in which Y is a phosphate group.
Another particularly preferred group of compounds are those of formula II in which Y is a group NR5C(O)R4, R5 is hydrogen and R4 is a 1-aminoalkyl group which can be further substituted for example by a hydroxy group.
Where one or more functional groups in compounds of formula I or II are sufficiently basic or acidic the formation of salts is possible. Suitable salts include pharmaceutically acceptable salts for example acid addition salts including hydrochlorides, hydrobromides, phosphates, sulphates, hydrogen sulphates, alkylsulphonates, arylsulphonates, acetates, benzoates, citrates, maleates, fumarates, succinates, lactates and tartrates, salts derived from inorganic bases including alkali metal salts such as sodium or potassium salts, alkaline earth metal salts such as magnesium or calcium salts, and salts derived from organic amines such as morpholine, piperidine or dimethylamine salts.
Those skilled in the art will recognise that compounds of formulae I and II may exist as stereoisomers and/or geometrical isomers and accordingly the present invention includes all such isomers and mixtures thereof. The substituted benzimidazole group is capable of existing in tautomeric forms and the formulae I and II are intended to represent all tautomeric forms and the substituent AX- is in the 5(6) position.
Compounds of Formula I or II may be prepared by any process known to a person skilled in the art. Compounds of Formula I or II may be prepared by a number of processes as generally described below and more specifically in the Examples hereinafter. In the following process description, the symbols A, X and alk when used in the formulae depicted are to be understood to represent those groups described above in relation to formula I or II unless otherwise indicated. In the schemes described below it may be necessary to employ protecting groups which are then removed during the final stages of the synthesis. The appropriate use of such protecting groups and processes for their removal will be readily apparent to those skilled in the art.
Thus according to a further aspect of the invention compounds of formulae I and II in which R1 and R2 are hydrogen may be prepared by treatment of a diamine of formula III with a 1,3-bis(alkoxycarbonyl)-S-alkyl isothiourea, for example 1,3-bis(methoxycarbonyl)-S-methyl isothiourea or 1,3-bis(ethoxycarbonyl)-S-methyl isothiourea, in a solvent such as an alcohol, for example methanol or ethanol, optionally mixed with water, at from about room temperature to the reflux temperature of the solvent for about 5 minutes to 6 hours. The reaction medium is preferably made acidic by the addition of for example an organic acid such as acetic acid or p-toluenesulphonic acid. 
Compounds of formula III are either known or can be prepared by conventional procedures.
Compounds of formulae I and II can also be prepared from other compounds of formulae I and II by chemical modification. Example of such chemical modifications that may be applied are standard alkylation, acylation, reduction, oxidation, sulphation, aromatic halogenation, aromatic nitration, phosphorylation, hydrolysis, condensation, cleavage and coupling reactions. These reactions may be used to add new substituents, to modify existing substituents or to modify other parts of the molecule.
Thus for example a compound of formula I or II in which R1 is hydrogen can be converted into the corresponding compounds where R1 is alkylaminocarbonyl by treatment with an alkyl isocyanate in a solvent such as tetrahydrofuran at a temperature in the range 0xc2x0 to 40xc2x0 C., typically room temperature.
In another general example a thioether group in a compound of formula I or II can be converted into a sulphinyl group by treatment with periodate in an aqueous alcohol solvent such as aqueous methanol or in aqeuous acetonitrile at about xe2x88x9220xc2x0 to 50xc2x0 C., for about 1 to 16 h. Alternatively this conversion can be effected by treatment with one equivalent of a peracid such as 3-chloroperbenzoic acid in a chlorinated solvent such as dichloromethane or chloroform, at a temperature of about xe2x88x9230xc2x0 C. to room temperature.
In a further general example a thioether group in a compound of formula I or II can be converted into a sulphonyl group by treatment with two or more equivalents of a peracid such as 3-chloroperbenzoic acid in a chlorinated solvent such as dichloromethane or chloroform, at a temperature of about xe2x88x9230xc2x0 C. to room temperature.
In a further general example a keto group in a compound of formula I or II can be converted into a carbinol group by treatment with a reducing agent for example a hydride such as lithium aluminium hydride in an ether solvent such as diethyl ether or tetrahydrofuran at a temperature of from about 0xc2x0 to the reflux temperature of the solvent.
In a further general example a keto group in a compound of formula I or II can be converted into an imine by treatment with ammonia in an alcoholic solvent such as ethanol at around room temperature for an extended period, for example three weeks.
In a further general example a keto group in a compound of formula I or II can be converted into an oxime by treatment with hydroxylamine in an alcoholic solvent such as ethanol at around room temperature to around the reflux temperature of the solvent.
In a further general example a compound of formula I or II containing a hydroxy group can be converted into the corresponding dihydrogenphosphate ester by treatment with for example di-tert-butyl diethylphosphoramidite in the presence of a suitable catalyst for example tetrazole in a solvent such as an ether solvent for example tetrahydrofuran at a temperature in the range xe2x88x9240 to 40xc2x0 C., conveniently at or near room temperature, followed by treatment with an oxidising agent for example 3-chloroperoxy benzoic acid or magnesium monoperoxyphthalate at a temperature in the range xe2x88x9278xc2x0 C. to 40xc2x0 C. preferably xe2x88x9265 to xe2x88x9210xc2x0 C. The resulting intermediate phosphate triester is treated with an acid for example trifluoroacetic acid in a solvent such as a chlorinated solvent e.g. dichloromethane at a temperature in the range xe2x88x9230 to 40xc2x0 C. conveniently at or near 0xc2x0 C. to give the compound of formula I or II containing a dihydrogenphosphate-ester.
In another general example an O-alkyl group may be cleaved to the corresponding alcohol (OH) by reaction with boron tribromide in a solvent such as a chlorinated solvent e.g. dichloromethane at a low temperature e.g. around xe2x88x9278xc2x0 C.
In a further general example compounds of formula I or II may be alkylated by reaction with a suitable alkylating agent such as an alkyl halide, an alkyl toluenesulphonate, an alkyl methanesulphonate or an alkyl triflate. The alkylation reaction can be carried out in the presence of a base for example an inorganic base such as a carbonate e.g. caesium or potassium carbonate, a hydride such as sodium hydride or an alkoxide such as potassium t-butoxide in a suitable solvent such as an aprotic solvent e.g. dimethylformarnide or an ether solvent such as tetrahydrofuran at a temperature of around xe2x88x9210 to 80xc2x0 C.
In a further general example compounds of formula I or II containing an amine group may be acylated by treatment with a carboxylic acid and a coupling reagent, for example dicyclohexylcarbodiimide, in a sutable solvent for example an aprotic solvent such as dimethylformamide, an ether solvent such as tetrahydrofuran, a chlorinated solvent for example dichloromethane or a solvent mixture at a temperature in the range 0xc2x0 to 60xc2x0, preferably about room temperature.
In a further general example a compound of formula I or II containing an OH group can be converted into a carbamate by reaction with an alkyl isocyanate or a carbamoyl chloride in an aprotic solvent such as dimethylfornamide, an ether solvent such as tetrahydrofuran, a chlorinated solvent for example dichloromethane or a solvent mixture in the presence of a base such as a tertiary amine base for example triethylamine at a temperature in the range xe2x88x9220xc2x0 to the reflux temperature of the solvent, conveniently at or around room temperature.
In a further general example a compound of formula I or II containing an amino group can be converted into a urea by reaction with an isocyanate or a carbamoyl chloride in an aprotic solvent such as dimethylformamide, an ether solvent such as tetrahydrofuran, a chlorinated solvent for example dichloromethane or a solvent mixture in the presence of a base such as a tertiary amine base for example triethylamine at a temperature in the range xe2x88x9220xc2x0 C. to the reflux temperature of the solvent, conveniently at or around room temperature.
In a further general example a compound of formula I or II containing a hydroxy group can be converted into a carbonate by reaction with an chloroformnate in an aprotic solvent such as dimethylformamnide, an ether solvent such as tetrahydrofuran, a chlorinated solvent for example dichloromethane or a solvent mixture in the presence of a base such as a tertiary amine base for example triethylamine at a temperature in the range xe2x88x9220xc2x0 C. to the reflux temperature of the solvent, preferably at or around 0xc2x0 C.
Preparation of a compound of formula I or II as a single enantiomer or, where appropriate, diastereomer may be effected by synthesis from an enantiomerically pure starting material or intermediate or by resolution of the final product in a conventional manner.
Acid addition salts of the compounds of formula I or II are prepared in a conventional manner by treating a solution or suspension of the free base I or II with about one equivalent of a pharmaceutically acceptable acid. Salts of compounds of formula I or II derived from inorganic or organic bases are prepared in a conventional manner by treating a solution or suspension of the free acid I or II with about one equivalent of a pharmaceutically acceptable organic or inorganic base. Alternatively both acid addition salts and salts derived from bases may be prepared by treatment of the parent compound with the appropriate ion-exchange resin in a standard fashion. Conventional concentration and recrystallisation techniques are employed in isolating the salts.
Compounds according to the invention are able to destroy vasculature that has been newly formed, for example tumour vasculature, while leaving unaffected normal, mature vasculature. The ability of the compounds to act in this way may be determined by the tests described hereinafter.
The compounds according to the invention are thus of particular use in the prophylaxis and treatment of cancers involving solid tumours and in the prophylaxis and treatment of diseases where inappropriate angiogenesis occurs such as diabetic retinopathy, psoriasis, rheumatoid arthritis, atherosclerosis and macular degeneration.
The compounds of the invention may be administered as a sole therapy or in combination with other treatments. For the treatment of solid tumours compounds of the invention may be administered in combination with radiotherapy or in combination with other anti-tumour substances for example those selected from mitotic inhibitors, for example vinblastine, paclitaxel and docetaxel; alkylating agents, for example cisplatin, carboplatin and cyclophosphamide; antimetabolites, for example 5-fluorouracil, cytosine arabinoside and hydroxyurea; intercalating agents for example adriamycin and bleomycin; enzymes, for example aspariginase; topoisomerase inhibitors for example etoposide, topotecan and irinotecan; thymidylate synthase inhibitors for example raltitrexed; biological response modifiers for example interferon; antibodies for example edrecolomab and antibodies against the EGFr, HER2 receptor or VEGF receptor: and anti-hormones for example tamoxifen. Such combination treatment may involve simultaneous or sequential application of the individual components of the treatment.
For the prophylaxis and treatment of disease the compounds according to the invention may be administered as pharmaceutical compositions selected with regard to the intended route of administration and standard pharmaceutical practice. Such pharmaceutical compositions may take a form suitable for oral, buccal, nasal, topical, rectal or parenteral administration and may be prepared in a conventional manner using conventional excipients. For example for oral administration the pharmaceutical compositions may take the form of tablets or capsules. For nasal administration or administration by inhalation the compounds may be conveniently delivered as a powder or in solution. Topical administration may be as an ointment or cream and rectal administration may be as a suppository. For parenteral injection (including intravenous, subcutaneous, intramuscular, intravascular or infusion) the composition may take the form of, for example, a sterile solution, suspension or emulsion.
The dose of a compound of the invention required for the prophylaxis or treatment of a particular condition will vary depending on the compound chosen, the route of administration, the form and severity of the condition and whether the compound is to be administered alone or in combination with another drug. Thus the precise dose will be determined by the administering physician but in general daily dosages may be in the range 0.001 to 100 mg/kg preferably 0.1 to 50 mg/kg.
The following test was used to demonstrate the activity and selectivity of compounds according to the invention.
The following experiment demonstrates the ability of the compounds to damage tumour vasculature.
Tumour functional vascular volume in CaNT tumour-bearing mice was measured using the fluorescent dye Hoechst 33342 according to the method of Smith et al (Brit J Cancer 57, 247-253, 1988). The fluorescent dye was dissolved in saline at 6.25 mg/ml and injected intravenously at 10 mg/kg 6 hours or 24 hours after intraperitoneal drug treatment. One minute later, animals were killed and tumours excised and frozen; 10 xcexcm sections were cut at 3 different levels and observed under UV illumination using an Olympus microscope equipped with epifluorescence. Blood vessels were identified by their fluorescent outlines and vascular volume was quantified using a point scoring system based on that described by Chalkley, (J Natl Cancer Inst, 4, 47-53, 1943). All estimates were based on counting a minimum of 100 fields from sections cut at the 3 different levels. Results are expressed as percentage reduction in vascular volume compared to control.
The activity of compounds of the invention in this assay is shown in Table 1.